Technological advances have significantly changed telecommunications. Particularly, telephone capabilities have changed dramatically over the last few years. A feature that has become readily available in both standard and cellular phones is caller identification (caller ID). Caller ID is a function of the telephone that allows a call recipient of the telephone to view information regarding the incoming call. Typically, a display associated with a call recipient's telephone, either integrated into the telephone itself or as a part of specifically tailored hardware (e.g., as an external display box) may display a telephone number and/or a name associated with an incoming call.
Depending on the characteristics of the individual system, caller ID may be utilized in certain call filtering applications. For example, based on caller ID data, a user can program a phone such as a voice over Internet protocol (VoIP) phone to block unwanted callers, automatically hang up, or play certain greeting messages. However, a user or an administrator has to configure the local phone system or the associated private branch exchange (PBX) system and specific known phone numbers have to be programmed to be associated with the call routing rules. If an incoming call is received with an unknown phone number, the call filtering operations may not be effective.